Which statement describes erythrocytes most accurately?

Which statement describes erythrocytes most accurately?

• A. Erythrocytes are pink, anucleate, lack organelles, and are biconcave discs that transport oxygen and carbon dioxide.
• B. Erythrocytes are nucleated cells that fight infection.
• C. Erythrocytes are large white blood cells involved in immunity.
• D. Erythrocytes are platelets involved in clotting.

Answer: (A)

The main concept is that erythrocytes are specialized for efficient gas transport. Mature human red blood cells have no nucleus and lack other organelles, which frees space to pack hemoglobin. Their biconcave shape increases surface area, speeding up the diffusion of oxygen into and carbon dioxide out of the blood. Hemoglobin binds oxygen in the lungs (giving a pink color when oxygenated) and releases it to tissues, then picks up carbon dioxide from tissues to be exhaled. This combination—pink color, anucleate, no organelles, and biconcave discs optimized for gas transport—best describes erythrocytes. In contrast, descriptions involving nucleated cells that fight infection or platelets involved in clotting refer to other blood components, not red blood cells.

The main concept is that erythrocytes are specialized for efficient gas transport. Mature human red blood cells have no nucleus and lack other organelles, which frees space to pack hemoglobin. Their biconcave shape increases surface area, speeding up the diffusion of oxygen into and carbon dioxide out of the blood. Hemoglobin binds oxygen in the lungs (giving a pink color when oxygenated) and releases it to tissues, then picks up carbon dioxide from tissues to be exhaled. This combination—pink color, anucleate, no organelles, and biconcave discs optimized for gas transport—best describes erythrocytes. In contrast, descriptions involving nucleated cells that fight infection or platelets involved in clotting refer to other blood components, not red blood cells.